High altitude antenna



Jan. 27, 1953 Filed April 25, 1945 A. s. KAND OIAN EIAL 2,627,026

HIGH ALTITUDE ANTENNA 2 SHEETS-SHEET 2 sy/jv/zwy? ATTORAEY Patented Jan.27, 1 953 HIGH ALTITUDE ANTENNA Armig G. Kandoian, New York, N. Y., andRobert A. Felsenheld, East Orange, N. J assignors to Federal Telephoneand Radio Corporation, New York, N. Y., a corporation of DelawareApplication April 23, 1945, Serial No. 589,901 7 Claims. (01. 250-33)This invention relates to antennas and more particularly to antennas foraircraft transmittin radio signals at high altitudes.

In certain radio communication applications especially those involvingpulse type signals, high peak voltages of the order of to kilovolts areplaced on the transmitter antenna in the form of standing waves. Whensuch transmitters are used on planes at high altitudes, say 40 to 50thousand feet, with a corresponding decrease in ambient atmosphericpressure, the phenomenon known as corona discharge occurs, that is, theair near the high voltage point of the antenna or radiator becomesionized. In consequence of this ionization, a loss in power and in theemciency of transmission takes place.

To overcome this difliculty, numerous attempts have been made,particularly of molding low-loss dielectric materials over and on toantennas. The results, however, always proved unsatisfactory because ofretained air bubbles or cracks in'the insulation occurring near theradiator due to temperature effects, causing a corona loss or actualvoltage breakdown.- A

A solution arrived at by us, according to our invention included theprovision of a dielectric type cover for the radiator forming a sealedair chamber between the radiator and the cover.

It is accordingly an object of our invention to provide electro-magneticenergy radiatorrmeans for effective use at high altitudes.

It is also an object to provide a radiator with a structure for use athigh altitudes, such that the radiator is housed in a medium whosecondltions simulate atmospheric conditions at sea level.

It is a further object to provide a radiator and its immediatesurrounding elements such that, at high altitudes and at high voltages,the transmission efficiency and losses will be commensurate with thoseat sea level.

It is a further object to provide a radiator or antenna in a gaseousmedium such as air which is maintained substantially at atmosphericpressure at all altitudes.

It is a still further object to provide a radiator structure which willaccomplish the objects set forth above;

In accordance with the invention, we provide an ultra-high frequencyantenna with a dielectric housing which forms a pressurized hermeticallysealed air chamber about the radiator which permits high altitudeoperation without dielectric breakdown. The antenna is preferably fedfrom a conventional coaxial cable provided with a pressurized connectorfor junction to the output coupling of a suitable oscillator unit.

These and other features and objects of the invention may be betterunderstood from the fol-.

dipole type antenna in accordance with the invention;

Fig. 2 is a partial plan view of the antenna of Fig. 1; and

Fig. 3 is a view in vertical section of a horizontal dipole antennaincorporating our invention.

In the View of Fig. 1 there is shown a portion of a solid dielectrictype coaxial cable I having an outer insulating jacket 2, an outertubular conductor in the form of a metallic braid 3, a solid dielectric4, and an inner concentrically arranged conductor 5. A bared end of theconductor 5 is secured within an aperture 6 of a solid, conducting rod 1which may be of aluminum and which serves as a radiator or antenna inthis instance. A set screw 8 has been provided in the antenna 1 tosecure the conductor 5 within the antenna. It will be noted that thelower end 9 of the radiator rod 1 is resting on the squared end face ofthe solid dielectric 4 which extends through a passage [0 and a recess Hof an electro-conductive base or supporting member l2. The conductivebraid 3, which is shown freed of insulation over a certain portionthereof, has been flared outwardly and is held clamped adjacent anotherface [3 of the base member l2 by means of a flange member 14 which isheld secured to said base member by means of screws of which only one isshown at [5. The member [4 is provided with an axial passage I6 topermit the cable to passtherethrough, the passage being widened into arecess I! to retain therein a rubber bushing [8 which may be compressedupwardly toward the narrow portion of the recess by means of a nut 19which is movable on the member [4 on the threads 20 and which iseffective in pressing upwardly the bushing l8 by means of action on aretaining ring 2|; The bushing member is also provided with an axialaperture 22 to allow the passage of the cable I. This rubber bushingserves as an additional pressure seal for the antenna structure at thispoint. 1

The member M is electro-conductive so that a grounding circuit is thusestablished from the braided conductor 3, thru the member I2 to adiscoid member 23 which serves as the antenna counterpoise. The member23 may be secured ator 'l. The major portion of the chamber 21, however,has a diameter somewhat larger than that of the rod 7 so that an annularchamber is formed between the rod and-the housing along most of theirlength. The housingadjacent its open end is formed with an annular"projection 30, which extends with a close fit into 'the'recess ll ofthe member l2, wherein'the' hcusingimaybe held secured by means of asuitable cement as shown at 3|. with a flanged portion 32-='-near itsopen end, the faceof which is-madeto adjoin the top ofthe member I2,andwhereto it may be held secured byimeans of screws around itsperiphery such asthe'one'sho'wnat33. As may be seen in Fig. 2,

the'housing may take a-streamlined configuration if the'antenna' is usedin a--location where such form is of advantage as on the outside of theairplane.

I'n'Fi'gi 3 an embodiment of the invention is shown applied to the twoportions of a half wave horizontal dipole. A- coaxial cable, which issimilarly. constituted as the cable I in Figs 1, is shown having itsconductive braid connected to a tubular radiating member 35 by means ofa clamping member Edwhich is disposed within a'radiator supportingmember 31. The radiating member 35 is disposed at right angles to itssupport 31. A central conductor 38 of the cable 3 4 is shown freed ofits insulation to a considerable extent and held in conductive contactwithin a secondradiating'tubular member 39 by means of a cable clamp 40which is disposed Within: the radiator 39 and held therein by meansofset screws" 41; The entire central portion of the above describedstructure is enclosed in polyethylene'forming a contiguous housing 42for the central'portion and leaving-the ends of the radiato'rs 35 and39to' extend therebeyond. The housing 42 may if convenient be molded orpotted overthesaid central portion of the radiating structure. Thehousing is provided at both ends with threads and 44 which'servetoreceive thereon the'chambere'd housing members'of polyethylene 45' and46. A flanged member 4'! may be mounted on the cable 34'immediatelyadjacent'and underneath the radiator support 3'! forthesupport of the radiating structure.-

The form of antenna shown in Fig. 1 is of the type known as abroad bandquarter wave antenna for an ultra-high frequency band. It is assembledas a hermetically sealed unit and provided with an air cavity betweenthe radiator and the housing within which air has been trapped at sealevel-pressure. The housing is sealed to the base'member forming apressurized chamber about the radiator so that voltage breakdown at highaltitudeis eliminated since the antenna is always" surrounded by normalatmospheric pressure'. Due to the cavity a wide range of temperaturesmay also be endured by the structure without cracking. or otherdeleterious effects which maybe due to different temperaturecoefficients.

The transmission'line or cable may connect through a so=ca11edpressurizedconnectortdan The housing is also provided oscillator tominimize possible leakage along the conductors which is held to aminimum by provision of the cement 3| in the recess II and a rubberbushing 8 at the radiator base. This arrangement has been tested andfound to have eliminated the possibility of arcing or voltage breakdownup to altitudes of say, .40 to 50 thousand feet. The effectiveness ofthe radiator and its directive pattern is in nowise affected by thehousing.

In both cases illustrated the transmission of pulses will result in highvoltage points along the 'antennas sometimes as high as 5 to 10kilovolts.- Due to the dielectric constants of the aircavity and of thepolyethylene housing, the voltage radiant on the outside of the housingis below-the critical-value for causing corona, regardless of theatmospheric pressure effective outside; or altitude. The pressure withinthe cavity with a proper seal may be kept substantially 'at'the valueprevailingat sea level. for: all practicablealtitudes over an adequateperiod It will be seen therefore that with an antenna structureasdescribed above, the transmission of high voltage signals may beeffected at high altitudes without loss of efficiency due tovoltagebreakdown or leakage.

While we have shown two specific types of antennas andhousingsforproviding an efficient high voltage radiating means at all altitudes,any other type of antenna or antenna system suitable for therespectivecircumstances may besub stituted instead. Similarly many othervariations in the housings in accordance with ourinventionl will occurto those skilled in the art. Thespecific description of the particularembodiments is given above merely by way of illustration and is not tobe considered as a-limitation -of our: invention as indicated in theobjects thereof and defined in the appended claims.

We claim:

1. An electro-magnetic energy radiator structure for aircraft comprisinga radiator member, a rigid housing forming a chamber about said radiatormember inclosing a gaseous medium, and means for sealing said chamber tomaintain substantially constant sea level pressure in saidchamberregardless of changes in pressure outside said chamber.

2. An electro-magnetic energy radiator structure for aircraft comprisinga. coaxial cablehav ingan inner andan outer conductor, a radiatorforming an extension ofsaid inner conductor,

an-electro-conductive base member havingapas-- sage for said cable toextend therethrough, a counterpoise conductively secured to said basemember, said outer conductor being in conductive contact with said baseand thereby with said counterpoise, a rigid dielectric housing forming achamber about said radiator supported on said base, and means forhermetically sealing substantially-at sea level air pressure saidchamber and said radiator therein including said base and a portion ofsaid cable.

3. A radiator structure according to claim 2; further including meansfor forming a pressure seal about said cable secured tosaid base member.

4. An electro-magnetic radiator structure for aircraft comprising acoaxial cable having an outer and an inner conductor; a pair ofradiators disposed at right angles to the axis of said cable,'one ofsaid radiators being in electro-conductive connection with said inner,and said other radiator being'in connection with said outer conductor;means for supporting said pair of radiators out of electric contact withone another, and rigid housing means forming a, sealed pressure chamberapproximately at sea level pressure about each of said radiators.

5. An electro-magnetic radiator structure for aircraft comprising a pairof radiators disposed along one axis, means for supplying energy to saidpair of radiators, and rigid dielectric .housing means forming a sealedpressure chamber substantially at sea level pressure about saidradiators.

6. An electro-magnetio energy radiator for aircraft comprising aradiator member, a rigid housing forming a chamber about said radiatormember enclosing a gaseous medium at approximately sea level pressure, asolid dielectric cable connected to said radiator, and means sealingsaid chamber about said radiator member and a portion of said cableconnected thereto for maintaining the pressure about said radiatormember constant, said sealing means including a pressurized connectionabout said cable.

7. A radiator according to claim 6 in which said pressurized connectionincludes a seal be- 6 tween said housing and the solid dielectric ofsaid cable and a rubber bushing arranged between said outer conductorand said housing.

ARMIG G. KANDOIAN. ROBERT A. FELSENHELD.

REFERENCES CITED The following references are of record in the file ofthis patent:

